Cyrtodactylus bengkhuaiai, Purkayastha & Lalremsanga & Bohra & Biakzuala & Decemson & Muansanga & Vabeiryureilai & Chauhan & Rathee, 2021

Purkayastha, Jayaditya, Lalremsanga, Hmar Tlawmte, Bohra, Sanath Chandra, Biakzuala, Lal, Decemson, H. T., Muansanga, Lal, Vabeiryureilai, Mathipi, Chauhan, Suraj & Rathee, Yashpal Singh, 2021, Four new Bent-toed geckos (Cyrtodactylus Gray: Squamata: Gekkonidae) from northeast India, Zootaxa 4980 (1), pp. 451-489 : 474-478

Cyrtodactylus bengkhuaiai sp. nov.

Figs. 9 , 10 , 11d ; Appendix VI; Table 2

Holotype. Adult male ( MZMU1989 ), from Sailam Community Reserved Forest (23.342758°N, 92.800058°E; elevation 1372 m asl.), outskirts of Sailam village , Aizawl District , Mizoram state, northeast India, collected on 14 October 2020 by Lal Muansanga , Ht Decemson, Gospel Zothanmawia Hmar, and Fanai Malsawmdawngliana.

Paratypes. Two adult males ( MZMU1987 ; Figs. 5b , 7a ; MZMU1990 ), three adult females ( MZMU1985 ; MZMU1986 ; MZMU1988 ) , same collection details as holotype (Appendix VI) .

Definition. Cyrtodactylus bengkhuaiai sp. nov. is a moderate-sized gecko (adult SVL 54.9–72.5mm); 9–11 supralabials; 7–11 infralabials; dorsal tubercles are rounded, conical to weakly keeled and are in 22–26 longitudinal rows; 35–41 paravertebral tubercles; 37–42 mid-ventral scale rows; 5–7 precloacal pores in males; 15–19 subdigital lamellae under toe IV; no single row of transversely enlarged subcaudal scales; 7–9 pairs of dark brown blotches on the dorsum of the body.

Description of holotype ( Figs. 9 ). Holotype body curved clockwise, generally in a well-preserved condition.

Adult male, SVL 63.5 mm. Head longer than broad (HW/HL 0.65), little less than one-third of the SVL (HL/ SVL 0.31), distinct from neck. Loreal region inflated; interorbital area flat; canthus rostralis prominent, broadly rounded; snout is less than half of the head length (SO/HL 0.39), scales on the forehead, canthus rostralis and snout homogeneous. Scales from the posterior margin of the eyes to the nape are smaller than those of the forehead, somewhat blunt and juxtaposed; scales on the interorbital and occipital regions without distinct tubercles. Orbit diameter is less than one-quarter of the head length (OD/HL 0.19); pupil vertical with crenulate margins; supraciliaries small but distinct, somewhat blunt, median supraciliaries are the largest, decreasing in size anteriorly and posteriorly; ear opening small (EL/HL 0.08) oval, obliquely orientated; eye to ear distance is more than the eye diameter (OE/OD 1.4). Rostral wider than long (RL/RW 0.79), divided dorsally by a weakly developed rostral groove; single enlarged supranasal on either side, separated by two small internasals, about the same size as enlarged scales on the snout; rostral in contact with the first supralabials, nasals, supranasals and internasals; nostrils ovel, opening laterally orientated, posteriorly covered by the nasal pad, each nasal in broad contact with the rostral and surrounded by a supranasal, first supralabial, and three postnasals; three rows of scales separate the orbit from the supralabials; mental almost as wide as long (ML/MW 1.05), triangular; two well developed postmentals on either, the inner pair almost twice the size of the outer pair (PMIIL/PMIL 0.53); inner postmentals in contact with the mental, infralabial I, one outer postmental and four gular scales; outer postmental on each side is in contact with one inner postmental, infralabials I and II, and three gular scales; ten supralabials on each side bordered by a row of slightly elongated scales; ten infralabials on each side, infralabials I to IV bordered ventrally by a row of enlarged gular scales, largest anteriorly; gular region mostly covered with small granular scales except for a few rows bordering the mental, postmentals and infralabials which are larger, flat and juxtaposed.

Body moderately slender; trunk length is less than half of the snout to vent length (TRL/SVL 0.46); dorsal scales heterogeneous, mostly rounded granular scales, intermixed with enlarged tubercles, bluntly conical and feebly keeled throughout, becoming more conical towards the flanks, largest in the mid-body; tubercles extend posteriorly from the occipital region to beyond the tail base; tubercles on the nape are smaller than those on the dorsum; 24 mid-body rows of dorsal tubercles; 41 paravertebral tubercles between the level of the axilla and the level of the groin; ventrolateral folds poorly developed with a single row of smooth tubercles; ventral scales much larger than dorsals, smooth, cycloid, imbricate to subimbricate, largest on the abdomen, slightly smaller under the thighs and on the region anterior to the cloacal opening; 39 mid-ventral scale rows; 5 precloacal pores in a continous series; scales anteriorly and posteriorly bordering the pore-bearing scale series are also enlarged, slightly smaller than pore-bearing scales; three postcloacal tubercles on each side of the tail base.

Forearm (FL/SVL 0.15) short and tibia (CL/SVL 0.19) moderate; digits laterally compressed, without a scansorial pad, strongly inflected at each joint, all bearing robust, recurved claws; subdigital lamellae transversely widened beneath the basal phalanx; basal lamellae 4–5–5–7–4 on the left manus, 4–4–6–8–5 on the left pes; distal lamellae (intervening rows of nonlamellar granular scales between basal and distal lamellae series in parentheses): 7(1)–8(2)–9(3)–9(3)–7(2) on the left manus, 7(2)–8(3)–10(3)–10(3)–9(4) on the left pes; interdigital webbing absent from both the manus and pes; relative length of digits: I <V <II <III <IV on the left manus, I <II <III <V<IV on the left pes; scales on the palms and soles are smooth, weakly raised, subimbricate; scales on the forelimbs are heterogeneous in size, ventral portion covered with heterogenous sized imbricate scales; scales on the hindlimbs are heterogeneous in size, on dorsal surfaces of thighs and shanks with small granular scales, intermixed with scattered, enlarged, conical, feebly keeled tubercles; anterior portion of the thighs and ventral surfaces of hindlimbs with smooth and imbricate scales.

Tail regenerated from the second tail segment. Dorsal surface of the tail with small granular scales intermixed with tubercles and the ventral surface with small imbricate scales heterogeneous in size being larger in the middle. Three large conical tubercle present on each side of the ventral surface of at the tail base. No transversely enlarged subcaudal plates.

Colouration in life ( Fig. 10 ): Dorsal surface of the head is primarily yellowish brown with dark brown patches forming a reticulation pattern. Dark brown chevron marking on the nape. On the lateral side of the head, a prominent dark brown stripe runs from the snout to the eye passing through below the eye, terminating just above the ear opening. Ventral side of the head off white in colour without any markings. Dorsum yellowish brown with dark brown markings often bordered by white patches. Three dark brown stripes extend from behind the chevron marking of the nape to the axillary region. Dark brown blotches forming a pair runs along the body from just behind axilla to the groin. A total of seven pairs of such blotches are present. Ventral surface of the body off white in colour without any markings. Three fourth of the tail regenerated without any features. The dorsal surface of the original portion of the tail light brown with three pairs of dark brown markings as in the dorsum. Ventral surface of the tail of white in colour with intermittent dark patches limited to anterior portion of the tail.

Colouration in preservative ( Fig. 9 ; Appendix VI): The colour is pale in comparison to the live specimen. The dark spots on the dorsum have turned into lighter shades.

Variation. Refer to Table 2 for morphometric and basic pholidosis variation within the type series of Cyrtodactylus bengkhuaiai sp. nov. Specimen MZMU1986 has a meshed dorsal blotch pattern rather than elongated blotches. Females have pit bearing scales (4–5) in the precloacal region ( MZMU1985 : 5, MZMU1986 : 4, and MZMU1988 : 4) .

Comparison: Cyrtodactylus bengkhuaiai sp. nov. is a species of the mountain clade within the south of Brahmaputra clade (see Agarwal et al. 2018). Based on ND2 gene sequence Cyrtodactylus bengkhuaiai sp. nov. is sister to the above described C. aaronbaueri and C. montanus and differs by an uncorrected p-distance of 0.085 –0.121 from C. aaronbaueri and 0.108 –0.121 from C. montanus . Cyrtodactylus bengkhuaiai sp. nov. can be morphologically distinguished from C. aaronbaueri by having a lower TRL/SVL ratio (min 0.43, max 0.49, avg 0.46 versus min 0.5, max 0.56, avg 0.52 in C. aaronbaueri ). Except for single specimen (MZMU1990) with seven PcP Cyrtodactylus bengkhuaiai sp. nov. has the least number of PcP (5) of all the examined specimens (versus 7-8 in C. aaronbaueri ). Furthermore, female specimen of Cyrtodactylus bengkhuaiai sp. nov. have 4-5 pitted scales in precloacal region (versus 6-8 in C. aaronbaueri ). Morphologically, Cyrtodactylus bengkhuaiai sp. nov. can be differentiated from the following species by having a smaller maximum adult size, SVL 72.5, N =6 (versus C. kazirangaensis 80.0 mm, N =3; C. arunachalensis 81.7 mm, N=5; C. ayeyarwadyensis 78.0 mm, N =9; C. khasiensis 81.1 mm, N =7; C. martinstolli 82.0 mm, N =18; C. tamaiensis 90.0 mm, N =1; C. cayuensis 79.78 mm, N =18; C. urbanus 74.0 mm, N =7; C. jaintiaensis 96.2 mm, N =3; C. montanus 78.2 mm, N =5); from C. himalayicus by having a larger maximum adult size, SVL 72.5 mm, N =6 (versus 64.5 mm, N =2); Cyrtodactylus bengkhuaiai sp. nov. has the lowest number of precloacal pores in males, 5–7, N =6 (versus 10–11 PcP, N =3, in C. kazirangaensis ; 10–12 PcP, N = 7 in C. khasiensis ; 14 PcP, N = 2 in C. septentrionalis ; 9–12 PcP, N = 7 in C. urbanus ; 11–12 PcP, N =3, in C. jaintiaensis ; 8–10 PcP, N = 5 in C. montanus ; 7 PcP, N =2, in C. markuscombaii ; 10 PcP, N =2, in C. himalayicus ; 10–28 PcFP, N =25,in C. ayeyerwadyensis ; 26–39 PcFP, N =8, in C. guwahatiensis ; 29–37 PcFP, N =11, in C. tripuraensis and 40 PcFP, N =1, in C. tamaiensis . Cyrtodactylus bengkhuaiai sp. nov. has a higher MVSR, N =6 (37–42) than C. guwahatiensis , N =8(30–34); C. septentrionalis , N =2 (35–38); C. ayeyarwadyensis , N =25 (32-37); C. montanus , N =5(21-23); C. urbanus , N =7 (30–34) and C. nagalandensis N =2 (34–35). Cyrtodactylus bengkhuaiai sp. nov. has higher DTR, N =6 (22–26) in comparison to C. tripuraensis , N =11, (19–21); C. tamaiensis , N =1, (21); C. jaintiaensis , N =3, (19–20); C. nagalandensis , N =2 (16–18); C. himalayicus , N =2, (19–21); C. mandalayensis , N =1 (18); C. markuscombaii , N =2 (14–15). Cyrtodactylus bengkhuaiai sp. nov. differs from C. kazirangaensis , N =3 (11–12) by having a lower number of supralabials, N = 6 (9–11 in Cyrtodactylus bengkhuaiai sp. nov.). Cyrtodactylus bengkhuaiai sp. nov. does not have enlarged plate like scales in subcaudals, N =6 (versus present in C. khasiensis N =7; C. martinstoli , N =18 and C. cayuensis , N = 18). Cyrtodactylus bengkhuaiai sp. nov. has a single row of enlarged scales below PcP bearing scales (versus 3-4 rows of enlarged scales in C. arunachalensis , N=5).

Distribution and natural history ( Fig. 1 , Appendix VII). All specimens were encountered and collected during night surveys at ca. 18:30–23:00 hrs on 14 October 2020. The holotype of Cyrtodactylus bengkhuaiai sp. nov. was collected from a fern leaf near a slow flowing stream Sabual that discharged from a seasonal pond inside the Community Reserved Forest, near Sailam village. On the same day, other specimens (MZMU1985–1988) were collected from fissures and crevices of rocky walls along the same stream. One specimen (MZMU1990) was captured, from the rocky banks of Lengleh stream, inside the Community Reserved Forest. So far, the species is recorded only from its type locality in Sailam Community Reserved Forest, located ca. 77 km road distance south from Aizawl city, Mizoram. The type locality is a hilly region with an elevation range of approx. 1300–1440 m a.s.l., not far from Hmuifang Community Reserved Forest (ca. 11 km aerial distance north from Sailam), type locality of the recently discovered Mizoram endemic snake species Blythia hmuifang Vogel, Lalremsanga, Vanlalhrima, 2017 . Based on the terrain and elevation gradients, we expect the distribution of the species to be within a radius of at least 20 km, in the adjoining hill ranges starting from Hmuifang Community Reserved Forest to as far as Serchhip town, Serchhip District, Mizoram state.

Etymology. The specific epithet bengkhuaiai is an eponym honouring Bengkhuaia (~1830–1879), the Mizo chief of Sailam village, one of the most formidable chiefdoms.

Suggested common name. Bengkhuaiai bent-toed gecko.

Figures

FIGURE 1. Elevation map showing the type localities of new species and Cyrtodactylus species included in the comparisons: 1. Cyrtodactylus karsticola sp. nov. (black star); 2. C. agarwali sp. nov. (black circle); 3. C. aaronbaueri sp. nov. (black triangle); 4. C. bengkhuaiai sp. nov. (black tilted square); 5. C. montanus; 6. C. tripuraensis; 7. C. khasiensis; 8. C. jaintiaensis; 9. C. guwahatiensis; 10. C. urbanus; 11. C. septentrionalis; 12. C. kazirangaensis; 13. C. nagalandensis; 14. C. arunachalensis; 15. C. markuscombaii and C. martinstolli; 16. C. himalayicus; 17. C. cayuensis; 18. C. tamaiensis; 19. C. ayeyarwadyensis; 20. C. mandalayensis.

FIGURE 5. A: Dorsal view, B: ventral view, C: details of dorsal pholidosis, D: dorsal view of head, E: ventral view of head and F: lateral view of head of the holotype of Cyrtodactylus agarwali sp. nov. (MZMU2160)

FIGURE 7. A: Dorsal view, B: ventral view, C: details of dorsal pholidosis, D: dorsal view of head, E: ventral view of head and F: lateral view of head of the holotype of Cyrtodactylus aaronbaueri sp. nov. (MZMU2015)

FIGURE 9. A: Dorsal view, B: ventral view, C: details of dorsal pholidosis, D dorsal view of head, E: ventral view of head and F: lateral view of head of the holotype of Cyrtodactylus bengkhuaiai sp. nov. (MZMU1989)

FIGURE 10. Live specimens of Cyrtodactylus bengkhuaiai sp. nov. (uncollected specimen)

FIGURE 11. The arrangement of A: precloacofemoral pores in Cyrtodactylus karsticola sp. nov.; B: precloacal pores in Cyrtodactylus agarwali sp. nov.; C: precloacal pores in Cyrtodactylus aaronbaueri sp. nov.and D: precloacal pores in Cyrtodactylus bengkhuaiai sp. nov.